Humidity is perhaps the most underrated growth factor. We use relative humidity RL as a unit to measure this and to make adjustments. A dry air will accelerate the evaporation of the moisture from the leaf and a very moist air will delay this. A plant must always evaporate some water so that there is room in the plant for new water from the medium in which new nutrients are dissolved.
The plant is like a pump that works on solar energy. However, if the RL is too low, the plant will evaporate more than it can absorb and the plant will experience a growth disorder and may eventually dry out. If the humidity is extremely high, the plant will eventually grow little.A balance in this is therefore very important. Small cuttings still have very little root and therefore cannot absorb much water. To make a cutting the hardest in the first 3 weeks you have to have an RL of about 80%. After that, up to and including approximately the 6th week, the optimum RL is 60%. In the 7th week and later we bring the RL down again but not lower than 40%. Below 40% the evaporation goes very fast, making it very difficult for the plant to get new moisture into the plant in time. The plant will close the stomata as a result of which the growth and flowering will stop. And downtime is always at the expense of the proceeds.
The humidity temperature is also important. There are systems that can easily blow cold water into the air. However, this cold moisture will naturally also slow down growth. It is best to use lukewarm water. Hobby growers who do not have a humidifier at their disposal can best spray the leaves regularly during the first 6 weeks.